深度学习3.2 线性回归的从零开始实现features[:, 1]: 选取所有样本的第二个特征(索引为1的列)。tensor([[ 1.6556, 0.1851], [-1.4880, 0.0684], [ 1.0536, 0.9818], [-0.7794, -1.9199], [-0.3383, 0.2244], [-0.2260, 3.1530], [-2.3626, 1.1877], [-0.3301, 0.1781], [-0.6136, -1.2974], [-0.3397, -0.2088]]) tensor([[ 6.8888